Characterization of Atherosclerotic
Plaque Components by AFM

Jacques Ohayon, PhD and Philippe Tracqui, PhD

Mapping
elasticity moduli of atherosclerotic plaque in situ via atomic force microscopy
- Journal of structural Biology, 174(1):115-23, 2011 - Several studies have suggested that evolving
mechanical stresses and strains drive atherosclerotic plaque development and
vulnerability. Especially, stress distribution in the plaque fibrous capsule is
an important determinant for the risk of vulnerable plaque rupture.
Knowledge of the stiffness of atherosclerotic plaque components is
therefore of critical importance. In this work, force mapping experiments using
atomic force microscopy (AFM) were conducted in apolipoprotein E-deficient (ApoE−/−)
mouse, which represents the most widely used experimental model for
studying mechanisms underlying the development of atherosclerotic lesions.To obtain the elastic material
properties of fibrous caps and lipidic cores of atherosclerotic plaques, serial
cross-sections of aortic arch lesions were probed at different sites.
Atherosclerotic plaque sub-structures were subdivided into cellular fibrotic,
hypocellular fibrotic and lipidic rich areas according to histological
staining. Hertz’s contact mechanics were used to determine elasticity (Young’s)
moduli that were related to the underlying histological plaque structure.
Cellular fibrotic regions exhibit a mean Young modulus of 10.4 ±
5.7 kPa. Hypocellular fibrous caps were almost six-times stiffer, with average
modulus value of 59.4 ± 47.4 kPa, locally rising up to ~ 250
kPa. Lipid rich areas exhibit a rather large range of Young’s moduli, with
average value of 5.5 ± 3.5 kPa. Such precise quantification of
plaque stiffness heterogeneity will allow investigators to have prospectively a
better monitoring of atherosclerotic disease evolution, including arterial wall
remodeling and plaque rupture, in response to mechanical constraints imposed by
vascular shear stress and blood pressure.